Each September, the Northern Hemisphere experiences the autumnal equinox, which marks the official beginning of fall. In the Southern Hemisphere, spring is arriving at this time.
Each year there are two equinoxes, the vernal and the autumnal (March and September, respectively). Shortly after the autumnal equinox, days begin getting shorter and the nights get longer. The autumnal equinox always occurs between Sept. 21 and Sept. 24. In 2021, the autumnal equinox is on Wednesday, Sept. 22.
The word equinox is from the Latin ‘aequi,’ meaning ‘equal,’ and ‘nox’ or ‘night.’ That means that during each equinox the hours of day and night are nearly equal in length across the planet. During the equinox, the part of the Earth that is closest to the sun is the equator, explains History.com. That helps make night and day equal in length. According to the Farmer’s Almanac, the Autumnal Equinox on Sept. 22, 2021, arrives at 3:21 p.m. EDT, 2:21 p.m. CDT, 1:21 p.m. MDT, and 12:21 p.m. PDT.